Torch for welding thermoplastic material



March 19, 1946. w. M PHILLIPS. JR

TORCH FOR WELDING THERMOPLASTIC MATERIAL Filed April 16, 1945 2 Sheets-Sheet l March 19, 1946. I w. M. PHILLIPS. JR 2,396,968

TORCH FOR WELDING THERMOPLASTIC MATERIAL Filed April 16, 1943 Sheets-Sheet 2 {L ydia 0 76-1 4% 7 6/ $7 52/ 1 VENTOR. (ll/Mam M. Phil qas ifi'.

BY *W Patented Mar. 19, 1946 TORCH FOR WELDING THERMOPLASTIC MATERIAL William M. Phillips, Jr., Detroit, Mich., assignor to The Udylite Corporation, Detroit, Mich., a

corporation of Delaware Application April 16, 1943, Serial N0. 483,364

2 Claims. (Cl. 263-19) This invention relates to a torch and more particularly to a torch which is useful in the welding of thermoplastic materials. In the copending application of Gunnar Lindh and William M.

Phillips, Jr., Serial No. 476,228, filed February 17,

1943, there is described a method for welding thermoplastic materials which uses a jet or blast of gas at a temperature sufficient to bring the thermoplastic substances being welded to their welding temperature.

This invention contemplates a torch which produces a. hot gaseous blast or jet which is efficient in operation, easily manipulated in the welding of thermoplastic sheets or articles, and which is simple in structure.

In welding thermoplastic materials it is essential that the materials should not be brought to their charring temperature. It is the object of this invention to produce a torch for welding -of thermoplastic materials in which the temperature of the hot gaseous blast can be easily ,controlled to avoid charring of the thermoplastic material being welded.

This invention also contemplates a light tool which gives an adequate supply of hot air or gas at high velocity. It is an object of this invention to produce a small, light weight, portable tool which can be easily manipulated either by hand or by a mechanical traversing mechanism.

Fig. 1 is a perspective showing the torch in welding position relative to the thermoplastic material being welded.

Fig. 2 is a longitudinal section through the torch.

, 4-4 and 55, respectively, of Fig. 2.

Fig. 5a shows a longitudinal section through a modified form of torch. Fig. 6 is a section along the line 5-6 of Fig. 5a. Fig. 7 is a, longitudinal section through the nozzle member of the torch shown in Fig. 5a.

Fig. 8 is a section along the line 8-8 of Fig. '7. Referring more particularly to the drawings it will be seen that the torch comprises a combustion tube I of any suitable material such as copper. Tube I is mounted within tube 2 and in spaced relation therewith to provide a passageway 3 for counter-current flow of one of the gases as explained below. Tube 2 likewise can be fabricated from any suitable material such as copper or steel.

Tube I is fixedly supported within tube 2 by means of spacing rings 4, 5 and 6 which preferably have a gas-tight seal along their inside circumference with tube I and along their outside circumference with the inside of tube 2. Thus, rings 4 and 5 cooperate with tubes I and 2 to form the passageway 3 and rings 5 and 6 cooperate with tubes I and 2 to form the passageway I.

A tubular casing 8 of steel or any other suit able material is positioned over the tube 2 and is Welded or otherwise secured thereto as at 9 to form a gas-tight joint. Casing 8 being spaced from tube 2 provides a passageway IIJ surrounding tube 2 through which a gas flows in countercurrent direction to the gas in passageway 3. Tube 2 is connected at one end by means of pipe line II with a source of gas I2 preferably under pressure. The flow of gas from source I2 into line II is controlled by a valve I3. A nozzle I4 is fixed within tube I and connected by means of pipe line I5 with another source of gas I6 under pressure. The flow of gas from source I5 into line I5 is controlled by valve II.

Passageway TI communicates with passageway II] by means of a plurality of orifices I8. Passageway In communicates with passageway 3 by means of a plurality of orifices I9, and passageway 3 communicates with the combustion chamber 20, that is, the interior of tube, I, by means of a plurality of orifices 2|. The orifices or jets 2| should be circumferentially spaced about the nozzle I4 and positioned upstream, that is, to the left of the nozzle outlet orifice 24, otherwise no flame will be produced in the combustion chamber. Tube I is provided with an outlet nozzle 22. The nozzle 22 preferably is provided with a flattened or elongated outlet 23 which spreads the hot gaseous blast flowing from the torch.

Various combustible gases can be burned i the torch to produce the gaseous blast of the temperature desired, such, for example, as hydrogen, acetylene, methane, ethylene, propane, and other hydrocarbon combustible gases, gasoline or .oil. For supporting combustion the preferred gas-is oxygen or air. The gas flowing from. outlet 23, however, should be inert with respect to the thermoplastic material being welded. The preferred combustible mixture consists of a mixture of by drogen and air.

The hydrogen is stored under high pressure in cylinder IB and fed through line I5 to nozzle l4..

rows; namely, the air flows from passageway I,

through ports I8 into and through passageway Ill and then through; ports I9 into passageway 3 wherein the air reverses its direction of flow as it through orifices 2| into the combustion chamber 20 wherein it mixes and burns with the hydrogen flowing from the nozzle M. The gaseous combustion products of the hydrogen and air, as well as some of the air which has not burned or chemically combined with the hydrogen, flows in counter-current direction to the air in chamber 3, as indicated by the arrows, and then out of the nozzle 22. Preferably more air passes into the combustion chamber than can chemically combine with the hydrogen. Thus issuing from nozzle 22 we have a hot gaseous blast comprising steam (the combustion product of hydrogen and oxygen) and hot air. The temperature of the gas blast issuing from outlet 22 will be controlled as described in the above-mentioned copending application, but in any event will be sufficiently high to melt or bring the thermoplastic materials to their welding temperature. The temperature of the blast flowing from nozzle 22 can be nicely controlled by means of valves l3 and I1. If the temperature of the gas flowing from the combustion chamber is too high, then valve 3 can be opened wider to admit more air into the combustion chamber and thus bring the temperature of the gases in the combustion chamber down, or valve I! can be turned to throttle down the amount of hydrogen flowing into the combustion chamber. In other words, by varying the relative amounts of hydrogen and air flowing combustion chamber 20 the temperature of the gas blast from outlet 22 can be raised or lowered and controlled as desired. The outlet orifice 22 for nozzle H is preferably positioned ahead or downstream from orifices 2| through which the air flows into the combustion chamber.

In a production torch of the type above shown and described, a number 2 jet was used for the hydrogen outlet 24 and this outlet was positioned I; of an inch ahead or downstream of six air inlet orifices 2| each 1 of an inch in diameter. The inside diameter of the brass combustion tube was of an inch and the length of the tube 6 inches. The wall thickness of the brasstube i was 1 of an inch and the space between tubes l and 2 was It; of an inch.

The counter-current flow of air through Dassageways J and 3 keeps the outside of the tool -in the manner taught in the above-mentioned co'pending application.

This tool or torch is useful for welding thermoplastic materials, and in particular for welding of the vinyl resins or thermoplastic polymerized vinyl compounds, such as Saran 3-115, a trade name for a copolymer of vinylidene chloride and vinyl chloride, Koroseal, a trade name for polymerized vinyl chloride plasticized with any of numerous well known organic plasticizers such as tricresyl phosphate or dioctyl phthalate, Saran F-125, a trade name for a copolymer of vinylidene chloride and vinyl cyanide, Vinylite, a trade name for a copolymer of vinyl chloride and vinyl acetate, polystyrene (polymerized styrene),

into the passes through passageway 3. The air then flows.

polymers of vinyl benzene, polymers of vinyl chloride, polymers of vinyl acetate.

This tool is also useful in the retreading of synthetic rubber tires. The new tread can be applied to the tire by directing'the hot gaseous blast against the surfaces to'be welded to bring them to their welding or joining temperature, thereby bonding the tread material to the tire.

, To provide the hot gaseous blast, this torch requires that a combustible gas or a mixture of a combustible gas and a gas which supports combustiorf should be supplied through nozzle ll to the combustion chamber 20. If only a combustible gas flows through nozzle M, then suflicient gas which supports combustion must be supplied around the stream of combustible gas through orifices 2|. If a mixture of a combustible gas and a gas which supports combustion containing less than the required amount of said latter gas flows through nozzle M, then suflicient gas to support combustion must be supplied through orifices 2| around this stream of gaseous mixture flowing from nozzle I4. The flame resulting from combustion in the combustion chamber 20 preferably should not strike the thermoplastic material because it will cause charring. Therefore, the buming gases are diluted in the combustion chamber either by an inert gas such as carbon dioxide, helium, or nitrogen, or by an excess of gas which supports combustion. By thus dilutin the hot products of combustion down to the temperature desired, one alsoobtains suflicient and the desired velocity of the heated gas or gaseous mixture flow ing from the nozzle 22. The velocity of the hot gas blast from nozzl 22 should not be sufiicient to blow away the melted thermoplastic material from the area being welded which obviously would render the weld ineffective. Whether the blast has suflicient velocity or force to blow away the 40 melted thermoplastic material can be readily ascertained by test and thus forms a very practical criterion for determining the proper velocity of the hot gas blast. If the velocity of the blast is such that it blows away the melted thermoplastic material, then the velocity of the blast should be slowed down belowthe velocity at which it blows away the melted thermoplastic. In regulating the heat output-of the torch and arriving at a suitable gas blast for welding thermoplastic material, several variables must be taken into consideration and all coordinated one with the other. These variables are: 1) melting point of the thermoplastic material being welded, (2) heat absorption coefficient of said thermoplastic material, (3) heat conductivity of said thermoplastic material, (4) temperature of the gas blast. (5) Velocity of the gas blast.

The flow of air or gas about the outside of tube preparatory to entering the combustion chamber serves a two-fold purpose; namely, this flow of air or gas cools down the outer casing 8 so that it can be readily handled by the operator without burning his hands and also pre-heats the gas or air entering the combustion chamber which obviously makes the torch more eflicient. Since the combustion chamber is insulated by the gas or airflow in tube 2, the combustion chamber can be located within the handle portion 8 of the torch. This materially cuts down the size of the torch and makes it more easily manipulated.

The modified form of the torch shown in Figs. 5a. to 7 comprises a tubular combustion chamber 30 which is surrounded by a tubular casing 3|. The combustion tube 30 is made from any suitable metal Or refractory material. Spacing rings 32, 33 and 34 support tube 30 within tube 3| and have gas tight joints with tubes 30 and 3|. A nozzle 35 is threaded into the end of the combustion chamber. In this form of the torcha removable nozzle assembly 36 is provided which can he slid into the end of tube 30 and removably retained therein byv a set screw 31. Assembly 36 has a gas tight fit with the tube 30. This nozzle assembly 36 is designed to inject a combustible mixture into the combustion chamber and to this end comprises a nozzle 38, an outer shell 39 and a mixing chamber 40. The mixing chamber 40 comprises a tubular member mounted within and in spaced relation with, shell 33 and provided with a plurality of orifices M. The end of tube 40 remote from nozzle 38 is connected by means of a tube or conduit 42 with a source of acetylene or other combustible gas under pressure. The shell 39 is connected by means of tube or conduit 43 with a source of gas under pressure which supports combustion, such, for example, as oxygen. The oxygen under pressure in shell 39 passes through orifices Bl into the mixing chamber where it intermixes with the acetylene to form a combustible mixture which'flows in a stream or jet from the outlet orifice 44 of nozzle 38 into the combustion chamber 30 where it burns.

As a diluent for controlling the temperature and the velocity of the gas blast from nozzle 38, air under pressure is supplied to the combustion chamber. To this end a source of air under pressure is connected by means of a tube or conduit 48 with one end of conduit 41. Conduit 41 is divided into two parts by means of a partition 48. Air flows from line 48 through opening 49 into chamber 50 between rings 33 and 34 and thus circulates about tube 30 to cool the end of this tube about the nozzle assembly 36. The air then flows through opening 5| in casing 3| back into conduit 41 in the direction indicated bythe arrows and then passes through opening 52 into casing 3lwhere it flows in a counter-current direction with the hot gases in combustion chamber 30. The air as thus pre-heated then passes through orifices 53 into the combustion chamber where it mixes with the hot gases of combustion preparatory to flowing from nozzle 35. Here again the flow of air on the outside of the combustion chamber preparatory to entering the same cools the outer casing 30 of the tool down so that it can be handled without burning the hands of the operator. This flow of air is also pre-heated before entering the combustion chamber and thereby increases the efiiciency oi the tool. This flow of air about the combustion chamber before entering the same also facilitates and makes possible the design of this tool so that it is relatively small in view of the high heat output of the same.

I claim:

- 1. A torch for producing a hot gaseous blast comprising an elongated combustion chamber having an inlet and an outlet at the other end, an elongated casing surrounding said combustion chamber and spaced therefrom to form a passageway about said combustion chamber said casing serving as a hand-grip, an inlet in said casing remote from the inlet in said combustion chamber,

means for introducing a combustible gas into said.

combustion chamber, and means for-introducin a gas under ressure which supports combustion through said inlet in the casing whereby said gas flows through said casing without the combustion chamber in counter-current and heat interchange relation with the gases in the combustion chamber preparatory to passing through the inlet into said combustion chamber whereby said gases intermix and the combustible gas burns, the said products of combustion being cooled by said heat interchange below their combustion temperature preparatory to flowing through the outlet of the combustion chamber in the form 0! a hot blast, the gas in said casing cooling the same to a sumciently low temperature for manually handling.

2. A torch for producing a hot gaseous blast comprising an elongated combustion chamberhaving a plurality of circumferentially spaced inlets at one end and an outlet at the other end, an elongated casing surrounding said combustion chamber and spaced therefrom to form a passageway about said combustion chamber, an inlet in said casing remote from the inlet in said combustion chamber, a second casing surrounding said first mentioned casing and serving as a hand grip, said second casing having an inlet remote from the inlet in the first casing, means for introducing a combustible gas into said combustion chamber, and means for introducing a gas under pressure which supports combustion through said inlet in the second casin whereby said gas flows through said second casing outside of said first casing and then through said inlet into the first casing without the combustion chamber in counter-current and heat interchange relation with the gases in the combustion chamber preparatory to passing through the inlet into said combustion chamber whereby said gases intermix and the combustible gas burns. the said products 01' combustion being cooled by said heat interchange preparatory to flowing through the outlet of the combustion chamber in the form of a hot blast. the gas in the second casing flowing in counter-current direction to the gas in the first casing, the gases flowing through said casings cooling the same and maintaining the temperature of the second casing sumciently low for manual handling of the torch.

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